When the drill cuttings exceed the volume of the borehole while hollow-stem auger drilling, you have usually...

When the drill cuttings exceed the volume of the borehole while hollow-stem auger drilling, you have usually...

• A. encountered flowing sand
• B. encountered bedrock
• C. encountered a clay lens
• D. encountered groundwater inflow only

Answer: (A)

When using hollow-stem auger drilling, the amount of drill cuttings returned to surface should roughly match the volume of material being removed from the hole. If you observe that the cuttings being brought up exceed the borehole’s volume, it signals material is flowing into the borehole from the surrounding formation. This is characteristic of flowing sands, where saturated, high-permeability sand layers allow sand grains to enter the hole under pressure and with the groundwater, causing a rapid influx of cuttings. Bedrock would not typically produce such a rapid, loose influx of cuttings; a clay lens would tend to restrict flow rather than fault the hole with a large, sand-rich influx; groundwater inflow alone without loose sand would bring water but not as many solid cuttings. So the best interpretation is encountered flowing sand.

When using hollow-stem auger drilling, the amount of drill cuttings returned to surface should roughly match the volume of material being removed from the hole. If you observe that the cuttings being brought up exceed the borehole’s volume, it signals material is flowing into the borehole from the surrounding formation. This is characteristic of flowing sands, where saturated, high-permeability sand layers allow sand grains to enter the hole under pressure and with the groundwater, causing a rapid influx of cuttings. Bedrock would not typically produce such a rapid, loose influx of cuttings; a clay lens would tend to restrict flow rather than fault the hole with a large, sand-rich influx; groundwater inflow alone without loose sand would bring water but not as many solid cuttings. So the best interpretation is encountered flowing sand.